30 BULLETIN 949, U. S. DEPARTMENT OF AGRICULTURE. 
which shall be on the center line both ways and the other two on the longitudinal 
center line and spaced 7 inches from the center each way. The rivet holes shall be 
countersunk on the face of the liner and the rivets shall be driven hot and chipped 
off flush with the surface of the liners. These liners shall be inspected from time to 
time, and if found loose shall be at once reriveted. 
Any test at the expiration of which a stave liner is found detached from the stave 
or seriously out of position shall be rejected. When a new rattler, in which a com- 
plete set of new staves is furnished, is first put into operation, it shall be charged with 
400 pounds of shot of the same sizes and in the same proportions as provided in sec- 
tion 9, and shall then be run for 18,000 revolutions at the usual prescribed rate of speed. 
The shot shall then be removed and a standard shot charge inserted, after which the 
rattler may be charged with brick for a test. 
No stave shall be used for more than 70 consecutive tests without renewing its 
lining. Two of the 14 staves shall be removed and relined at a time in such a way 
that of each pair, one falls upon one side of the barrel and the other upon the opposite 
side, and also so that the staves changed shall be consecutive but not contiguous, 
for example, 1 and 8, 3 and 10, 5 and 12, 7 and 14, 2 and 9, 4 and 11, 6 and 13, etc., 
to the end that the interior of the barrel at all times shall present the same relative 
condition of repair. The changes in the staves should be made at the time when 
the shot charges are being corrected, and the record must show the number of charges 
run since the last pair of new lined staves was placed in position . 
The staves when bolted to the heads shall form a barrel 20 inches long, inside meas- 
urement, between headliners. The liners of the staves shall be so placed as to drop 
between the headliners. The staves shall be bolted tightly to the heads by four three- 
fourths inch bolts, and each bolt shall be provided with a lock nut, and shall be in- 
spected at not less frequent intervals than every fifth test and all nuts kept tight. A 
record shall be made after each inspection showing in what condition the bolts were 
found. 
(8) The frame and driving mechanism. — The barrel shall be mounted on a cast-iron 
frame of sufficient strength and rigidity to support it without undue vibration. It shall 
rest on a rigid foundation with or without the interposition of wooden plates, and shall 
be fastened thereto by bolts at not less than four points. 
It shall be driven by gearing whose ratio of driver to driven is not less than one to 
four. The countershaft upon which the driving pinion is mounted shall not be less than 
1-^f inches in diameter, with bearing not less than 6 inches in length. If a belt drive 
is used the pulley shall not be less than 18 inches in diameter and 6| inches in face. 
A belt at least 6 inches in width properly adjusted, to avoid unnecessary slipping, 
should be used. 
(9) The abrasive charge. — The abrasive charge shall consist of cast-iron spheres of 
two sizes. When new, the larger spheres shall be 3.75 inches in diameter and shall 
weigh approximately 7.5 pounds (3.40 kg.) each. Ten spheres of this size shall be 
used. 
These shall be weighed separately after each 10 teste, and if the weight of any large 
sphere falls to 7 pounds (3.175 kg.) it shall be discarded and a new one substituted; 
provided, however, that all of the large spheres shall not be discarded and substi- 
tuted by new ones at any single time, and that so far as possible the large spheres 
shall compose a graduated series in various stages of wear. 
When new, the smaller spheres shall be 1.875 inches in diameter and shall weigh 
approximately 0.95 pound (0.43 kg.) each. In general, the number of small spheres 
in a charge shall not fall below 245 nor exceed 260. The collective weight of the large 
and small spheres shall be as nearly 300 pounds as possible. No small sphere shall 
be retained in use after it has been worn down so that it will pass a circular hole 
